An analytically derived whitecap coverage model

Joint probability function of local surface-particle and phase velocities is derived for a stationary Gaussian wave field with narrow-band spectrum.From the function a model of whitecap coverage is further derived by using tire kinematic condition (including the effect of drift current) for wave breaking.The drift current velocity in the model is then replaced by the friction velocity through an existing empirical formula.A coefficient in the model for relating temporal and spatial scales of wave breaking is determined by using an existing empirical formula of oceanic whitecap coverage and the well-known Pierson-Moskowitz spectrum.The main features of the model agree well with our general knowledge and observational evidence on wave breaking in deep waters.